diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 3e23cbb6..ca2cca57 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -156,7 +156,7 @@ bundle exec puma -C test/config/settings.rb test/rackup/hello.ru
 
 There is also a Dockerfile available for reproducing Linux-specific issues:
 ```sh
-docker build -f tools/docker/Dockerfile -t puma .
+docker build -f tools/Dockerfile -t puma .
 docker run -p 9292:9292 -it puma
 ```
 
diff --git a/tools/Dockerfile b/tools/Dockerfile
index af2fb0e2..bf616570 100644
--- a/tools/Dockerfile
+++ b/tools/Dockerfile
@@ -1,6 +1,6 @@
 # Use this Dockerfile to create minimal reproductions of issues
 
-FROM ruby:2.6
+FROM ruby:3.1
 
 # throw errors if Gemfile has been modified since Gemfile.lock
 RUN bundle config --global frozen 1